System and method for reducing blade exposures

ABSTRACT

Techniques for reducing blade exposures include one or more processors and a drive system configured to be coupled to a cutting instrument. The cutting instrument includes an end effector located at a distal end of the cutting instrument, the end effector comprising opposable gripping jaws and a cutting blade, a shaft configured to be coupled to the drive system, an articulated wrist coupling the end effector to the shaft and one or more drive mechanisms in the shaft for coupling force or torque from the drive system to the end effector and the articulated wrist. The one or more processors are configured to measure a jaw angle between the gripping jaws, measure articulation of the articulated wrist, correct the jaw angle based on the articulation of the articulated wrist, determine a cutting length based on the corrected jaw angle, and perform a cutting operation according to the cutting length.

RELATED APPLICATIONS

This patent application is a continuation of U.S. patent applicationSer. No. 15/573,031 filed on Nov. 9, 2017, which is a U.S. NationalStage patent application of International Patent Application No.PCT/US2016/032324 filed on May 13, 2016, which claims priority benefitof U.S. Provisional Patent Application titled “SYSTEM AND METHOD FORREDUCING BLADE EXPOSURES”, filed May 15, 2015 and having Ser. No.62/176,893. entitled each of which is incorporated by reference hereinin its entirety. The subject matter of these related applications ishereby incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates generally to operation of devices witharticulated arms and end effectors and more particularly to operation ofa minimally invasive cutting instrument so as to reduce blade exposures.

BACKGROUND

More and more devices are being replaced with autonomous andsemiautonomous electronic devices. This is especially true in thehospitals of today with large arrays of autonomous and semiautonomouselectronic devices being found in operating rooms, interventionalsuites, intensive care wards, emergency rooms, and the like. Forexample, glass and mercury thermometers are being replaced withelectronic thermometers, intravenous drip lines now include electronicmonitors and flow regulators, and traditional hand-held surgicalinstruments are being replaced by computer-assisted medical devices.

Minimally invasive surgical techniques using computer-assisted medicaldevices generally attempt to perform surgical and/or other procedureswhile minimizing damage to healthy tissue. Some minimally invasiveprocedures may be performed remotely through the use ofcomputer-assisted medical devices with surgical instruments. With manycomputer-assisted medical devices, a surgeon and/or other medicalpersonnel may typically manipulate input devices using one or morecontrols on an operator console. As the surgeon and/or other medicalpersonnel operate the various controls at the operator console, thecommands are relayed from the operator console to a patient side deviceto which one or more end effectors and/or surgical instruments aremounted. In this way, the surgeon and/or other medical personnel areable to perform one or more procedures on a patient using the endeffectors and/or surgical instruments. Depending upon the desiredprocedure and/or the surgical instruments in use, the desired proceduremay be performed partially or wholly under control of the surgeon and/ormedical personnel using teleoperation and/or under semi-autonomouscontrol where the surgical instrument may perform a sequence ofoperations based on one or more activation actions by the surgeon and/orother medical personnel.

Minimally invasive surgical instruments, whether actuated manually,teleoperatively, and/or semi-autonomously may be used in a variety ofoperations and/or procedures and may have various configurations. Manysuch instruments include an end effector mounted at a distal end of ashaft that may be mounted to the distal end of an articulated arm. Inmany operational scenarios, the shaft may be configured to be inserted(e.g., laparoscopically, thoracoscopically, and/or the like) through anopening (e.g., a body wall incision, a natural orifice, and/or the like)to reach a remote surgical site. In some instruments, an articulatingwrist mechanism may be mounted to the distal end of the instrument'sshaft to support the end effector with the articulating wrist providingthe ability to alter an orientation of the end effector relative to alongitudinal axis of the shaft.

End effectors of different design and/or configuration may be used toperform different tasks, procedures, and functions so as to be allow thesurgeon and/or other medical personnel to perform any of a variety ofsurgical procedures. Examples include, but are not limited to,cauterizing, ablating, suturing, cutting, stapling, fusing, sealing,etc., and/or combinations thereof. Accordingly, end effectors caninclude a variety of components and/or combinations of components toperform these surgical procedures.

Consistent with the goals of a minimally invasive procedure, the size ofthe end effector is typically kept as small as possible while stillallowing it to perform its intended task. One approach to keeping thesize of the end effector small is to accomplish actuation of the endeffector through the use of one or more inputs at a proximal end of thesurgical instrument, which is typically located externally to thepatient. Various gears, levers, pulleys, cables, rods, bands, and/or thelike, may then be used to transmit actions from the one or more inputsalong the shaft of the surgical instrument and to actuate the endeffector. In the case of a computer-assisted medical device with anappropriate surgical instrument, a transmission mechanism at theproximal end of the instrument interfaces with various motors,solenoids, servos, active actuators, hydraulics, pneumatics, and/or thelike provided on an articulated arm of the patient side device or apatient side cart. The motors, solenoids, servos, active actuators,hydraulics, pneumatics, and/or the like typically receive controlsignals through a master controller and provide input in the form offorce and/or torque at the proximal end of the transmission mechanism,which the various gears, levers, pulleys, cables, rods, bands, and/orthe like ultimately transmit to actuate the end effector at the distalend of the transmission mechanism.

Because of the remote nature of the operation of such end effectors, itmay be difficult in some cases for the surgeon and/or other medicalpersonnel to know the position of one or more components of the endeffector during actuation to perform a desired procedure. For example,in some cases, other portions of the surgical instrument, including theend effector itself, and/or parts of the anatomy of the patient may hidefrom view one or more components of the surgical instrument during theactuation of the one or more components. Additionally, when one or moreof the components encounters a fault condition while attempting toperform the desired procedure, it may be difficult for the surgeonand/or other medical personnel to detect and/or correct the faultcondition due to the limited visibility of the end effector, the limitedspace in which the surgical instrument operates, the limited access tothe surgical instrument, the remote position of the end effectorrelative to the surgeon and/or other medical personnel, and/or the like.

In addition, safety conditions may also be a factor in the design and/oroperation of the surgical instrument. In some examples, the end effectorof a surgical tool, such as a cutting tool, may include a sharp cuttingblade. When the cutting blade is not actively being used to cut, thecutting blade may be sheathed and/or garaged within a housing or garageon the end effector so that it is generally positioned where it cannotaccidentally cut tissue of the patient and/or medical personnelmanipulating the surgical tool during non-operation. Similarly, one ormore delicate components of the end effector may also be sheathed and/orgaraged to prevent damage to the delicate components duringnon-operation.

When the cutting blade is not able to be returned to the garage, anerror called a blade exposure may occur. In some cases, a blade exposuremay occur when tissue and/or other debris interfere with the path of thecutting blade toward the garage preventing retraction of the cuttingblade into the garage after a cutting operation. In some cases, a bladeexposure may occur when the cutting blade comes out of a groove or trackin the end effector used to guide the cutting blade preventingretraction of the cutting blade into the garage. It is generally a goodidea to avoid blade exposures as it is not always possible to correctthe blade exposure and retract the cutting blade into the garage withoutfirst extracting the cutting tool and end effector from within thepatient.

Accordingly, improved methods and systems for the operation of surgicalinstruments, such as a cutting instrument, are desirable. In someexamples, it may be desirable to reduce the likelihood of a bladeexposure.

SUMMARY

Consistent with some embodiments, a surgical cutting instrument for usewith a computer-assisted medical device includes an end effector locatedat a distal end of the surgical cutting instrument, one or more driveunits, a shaft coupled to the drive unit, an articulated wrist couplingthe end effector to the shaft, and one or more drive mechanisms in theshaft for coupling force or torque from the one or more drive units tothe end effector and the articulated wrist. The end effector includesopposable gripping jaws and a cutting blade. To perform a cuttingoperation, the surgical cutting instrument is configured to measure ajaw angle between the gripping jaws, measure articulation of thearticulated wrist, correct the jaw angle based on the articulation ofthe articulated wrist, determine a restriction on the cutting operationbased on the corrected jaw angle, and perform or prevent the cuttingoperation based on the restriction.

Consistent with some embodiments, a method of performing a cuttingoperation using a surgical cutting instrument for use with acomputer-assisted medical device includes measuring by one or moreprocessors and using one or more first sensors a jaw angle betweengripping jaws of an end effector of the surgical cutting instrument,measuring by the one or more processors and using one or more secondsensors articulation of an articulated wrist coupling the end effectorto a shaft of the surgical cutting instrument, correcting by the one ormore processors the jaw angle based on the articulation of thearticulated wrist, determining by the one or more processors arestriction on the cutting operation based on the corrected jaw angle,and performing or preventing the cutting operation based on therestriction.

Consistent with some embodiments, a non-transitory machine-readablemedium includes a plurality of machine-readable instructions which whenexecuted by one or more processors associated with a computer-assistedmedical device are adapted to cause the one or more processors toperform a method. The method includes measuring a jaw angle betweengripping jaws of an end effector of a surgical cutting instrumentoperated by the computer-assisted medical device, measuring articulationof an articulated wrist coupling the end effector to a shaft of thesurgical cutting instrument, correcting the jaw angle based on thearticulation of the articulated wrist, determining a restriction on thecutting operation based on the corrected jaw angle, and performing orpreventing the cutting operation based on the restriction using one ormore drive units.

Consistent with some embodiments, a computer-assisted medical deviceincludes one or more processors, an articulated arm, and a surgicalinstrument coupled to a distal end of the articulated arm. The surgicalinstrument includes an end effector located at a distal end of thesurgical instrument. The end effector includes opposable gripping jawsand a cutting blade. The surgical instrument further includes one ormore drive units located at a proximal end of the surgical instrument, ashaft coupled to the drive units, an articulated wrist coupling theshaft to the end effector, and one or more drive mechanisms in the shaftfor coupling force or torque from the one or more drive units to the endeffector and the articulated wrist. The computer-assisted medical deviceis configured to perform a cutting operation using the cutting blade bymeasuring a jaw angle between the gripping jaws, measuring articulationof the articulated wrist, correcting the jaw angle based on thearticulation of the articulated wrist, determining a restriction on thecutting operation based on the corrected jaw angle, and performing orpreventing the cutting operation based on the restriction.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified diagram of a computer-assisted system accordingto some embodiments.

FIG. 2 is a simplified diagram showing a minimally invasive surgicalinstrument according to some embodiments.

FIG. 3 is a simplified perspective diagram of the distal end of thesurgical instrument of FIG. 2 according to some embodiments.

FIGS. 4A-4C are simplified cut-away diagrams of the end effector ofFIGS. 2 and 3 according to some embodiments.

FIG. 5 is a simplified perspective diagram of a drive unit for a degreeof freedom according to some embodiments.

FIGS. 6A-6E are simplified diagrams of various side and front cut-awayviews of end effector and cutting blade configurations according to someembodiments.

FIGS. 7A and 7B are simplified diagrams of models of a probability ofblade exposure according to some embodiments.

FIG. 8 is a simplified diagram of an exemplary relationship betweenactual and measured jaw angle according to some embodiments.

FIG. 9 is a simplified diagram of a method for performing a cuttingoperation according to some embodiments.

In the figures, elements having the same designations have the same orsimilar functions.

DETAILED DESCRIPTION

In the following description, specific details are set forth describingsome embodiments consistent with the present disclosure. It will beapparent to one skilled in the art, however, that some embodiments maybe practiced without some or all of these specific details. The specificembodiments disclosed herein are meant to be illustrative but notlimiting. One skilled in the art may realize other elements that,although not specifically described here, are within the scope and thespirit of this disclosure. In addition, to avoid unnecessary repetition,one or more features shown and described in association with oneembodiment may be incorporated into other embodiments unlessspecifically described otherwise or if the one or more features wouldmake an embodiment non-functional.

FIG. 1 is a simplified diagram of a computer-assisted system 100according to some embodiments. As shown in FIG. 1 , computer-assistedsystem 100 includes a computer-assisted device 110 with one or moremovable or articulated arms 120. Each of the one or more articulatedarms 120 may support one or more instruments 130. In some examples,computer-assisted device 110 may be consistent with a computer-assistedsurgical device. The one or more articulated arms 120 may each providesupport for medical instruments 130 such as surgical instruments,imaging devices, and/or the like. In some examples, the instruments 130may include end effectors that are capable of, but are not limited to,performing, gripping, retracting, cauterizing, ablating, suturing,cutting, stapling, fusing, sealing, etc., and/or combinations thereof.

Computer-assisted device 110 may further be coupled to an operatorworkstation (not shown), which may include one or more master controlsfor operating the computer-assisted device 110, the one or morearticulated arms 120, and/or the instruments 130. In some examples, theone or more master controls may include master manipulators, levers,pedals, switches, keys, knobs, triggers, and/or the like. In someembodiments, computer-assisted device 110 and the operator workstationmay correspond to a da Vinci® Surgical System commercialized byIntuitive Surgical, Inc. of Sunnyvale, Calif. In some embodiments,computer-assisted surgical devices with other configurations, fewer ormore articulated arms, and/or the like may be used withcomputer-assisted system 100.

Computer-assisted device 110 is coupled to a control unit 140 via aninterface. The interface may include one or more cables, fibers,connectors, and/or buses and may further include one or more networkswith one or more network switching and/or routing devices. Control unit140 includes a processor 150 coupled to memory 160. Operation of controlunit 140 is controlled by processor 150. And although control unit 140is shown with only one processor 150, it is understood that processor150 may be representative of one or more central processing units,multi-core processors, microprocessors, microcontrollers, digital signalprocessors, field programmable gate arrays (FPGAs), application specificintegrated circuits (ASICs), and/or the like in control unit 140.Control unit 140 may be implemented as a stand-alone subsystem and/orboard added to a computing device or as a virtual machine. In someembodiments, control unit 140 may be included as part of the operatorworkstation and/or operated separately from, but in coordination withthe operator workstation.

Memory 160 may be used to store software executed by control unit 140and/or one or more data structures used during operation of control unit140. Memory 160 may include one or more types of machine readable media.Some common forms of machine readable media may include floppy disk,flexible disk, hard disk, magnetic tape, any other magnetic medium,CD-ROM, any other optical medium, punch cards, paper tape, any otherphysical medium with patterns of holes, RAM, PROM, EPROM, FLASH-EPROM,any other memory chip or cartridge, and/or any other medium from which aprocessor or computer is adapted to read.

As shown in FIG. 1 , memory 160 includes a control application 170 thatmay be used to support autonomous, semiautonomous, and/or teleoperatedcontrol of computer-assisted device 110. Control application 170 mayinclude one or more application programming interfaces (APIs) forreceiving position, motion, force, torque, and/or other sensorinformation from computer-assisted device 110, articulated arms 120,and/or instruments 130, exchanging position, motion, force, torque,and/or collision avoidance information with other control unitsregarding other devices, and/or planning and/or assisting in theplanning of motion for computer-assisted device 110, articulated arms120, and/or instruments 130. In some examples, control application 170may further support autonomous, semiautonomous, and/or teleoperatedcontrol of the instruments 130 during a surgical procedure. And althoughcontrol application 170 is depicted as a software application, controlapplication 170 may be implemented using hardware, software, and/or acombination of hardware and software.

In some embodiments, computer-assisted system 100 may be found in anoperating room and/or an interventional suite. And althoughcomputer-assisted system 100 includes only one computer-assisted device110 with two articulated arms 120 and corresponding instruments 130, oneof ordinary skill would understand that computer-assisted system 100 mayinclude any number of computer-assisted devices with articulated armsand/or instruments of similar and/or different in design fromcomputer-assisted device 110. In some examples, each of thecomputer-assisted devices may include fewer or more articulated armsand/or instruments.

FIG. 2 is a simplified diagram showing a minimally invasive surgicalinstrument 200 according to some embodiments. In some embodiments,surgical instrument 200 may be consistent with any of the instruments130 of FIG. 1 . The directions “proximal” and “distal” as depicted inFIG. 2 and as used herein help describe the relative orientation andlocation of components of surgical instrument 200. Distal generallyrefers to elements in a direction further along a kinematic chain from abase of a computer-assisted device, such as computer-assisted device110, and/or or closest to the surgical work site in the intendedoperational use of the surgical instrument 200. Proximal generallyrefers to elements in a direction closer along a kinematic chain towardthe base of the computer-assisted device and/or one of the articulatedarms of the computer-assisted device.

As shown in FIG. 2 , surgical instrument 200 includes a long shaft 210used to couple an end effector 220 located at a distal end of shaft 210to where the surgical instrument 200 is mounted to an articulated armand/or a computer-assisted device at a proximal end of shaft 210.Depending upon the particular procedure for which the surgicalinstrument 200 is being used, shaft 210 may be inserted through anopening (e.g., a body wall incision, a natural orifice, and/or the like)in order to place end effector 220 in proximity to a remote surgicalsite located within the anatomy of a patient. As further shown in FIG. 2, end effector 220 is generally consistent with a two-jawedgripper-style end effector, which in some embodiments may furtherinclude a cutting and/or a fusing or sealing mechanism as is describedin further detail below with respect to FIGS. 3 and 4A-4C. However, oneof ordinary skill would understand that different surgical instruments200 with different end effectors 220 are possible and may be consistentwith the embodiments of surgical instrument 200 as described elsewhereherein.

A surgical instrument, such as surgical instrument 200 with end effector220 typically relies on multiple degrees of freedom (DOFs) during itsoperation. Depending upon the configuration of surgical instrument 200and the articulated arm and/or computer-assisted device to which it ismounted, various DOFs that may be used to position, orient, and/oroperate end effector 220 are possible. In some examples, shaft 210 maybe inserted in a distal direction and/or retreated in a proximaldirection to provide an insertion DOF that may be used to control howdeep within the anatomy of the patient that end effector 220 is placed.In some examples, shaft 210 may be able rotate about its longitudinalaxis to provide a roll DOF that may be used to rotate end effector 220.In some examples, additional flexibility in the position and/ororientation of end effector 220 may be provided by an articulated wrist230 that is used to couple end effector 220 to the distal end of shaft210. In some examples, articulated wrist 230 may include one or morerotational joints, such as one or more roll, pitch or yaw joints thatmay provide one or more “roll,” “pitch,” and “yaw” DOF(s), respectively,that may be used to control an orientation of end effector 220 relativeto the longitudinal axis of shaft 210. In some examples, the one or morerotational joints may include a pitch and a yaw joint; a roll, a pitch,and a yaw joint, a roll, a pitch, and a roll joint; and/or the like. Insome examples, end effector 220 may further include a grip DOF used tocontrol the opening and closing of the jaws of end effector 220 and/oran activation DOF used to control the extension, retraction, and/oroperation of a cutting mechanism as is described in further detailbelow.

Surgical instrument 200 further includes a drive system 240 located atthe proximal end of shaft 210. Drive system 240 includes one or morecomponents for introducing forces and/or torques to surgical instrument200 that may be used to manipulate the various DOFs supported bysurgical instrument 200. In some examples, drive system 240 may includeone or more motors, solenoids, servos, active actuators, hydraulics,pneumatics, and/or the like that are operated based on signals receivedfrom a control unit, such as control unit 140 of FIG. 1 . In someexamples, the signals may include one or more currents, voltages,pulse-width modulated wave forms, and/or the like. In some examples,drive system 240 may include one or more shafts, gears, pulleys, rods,bands, and/or the like which may be coupled to corresponding motors,solenoids, servos, active actuators, hydraulics, pneumatics, and/or thelike that are part of the articulated arm, such as any of thearticulated arms 120, to which surgical instrument 200 is mounted. Insome examples, the one or more drive inputs, such as shafts, gears,pulleys, rods, bands, and/or the like, may be used to receive forcesand/or torques from the motors, solenoids, servos, active actuators,hydraulics, pneumatics, and/or the like and apply those forces and/ortorques to adjust the various DOFs of surgical instrument 200.

In some embodiments, the forces and/or torques generated by and/orreceived by drive system 240 may be transferred from drive system 240and along shaft 210 to the various joints and/or elements of surgicalinstrument 200 located distal to drive system 240 using one or moredrive mechanisms 250. In some examples, the one or more drive mechanisms250 may include one or more gears, levers, pulleys, cables, rods, bands,and/or the like. In some examples, shaft 210 is hollow and the drivemechanisms 250 pass along the inside of shaft 210 from drive system 240to the corresponding DOF in end effector 220 and/or articulated wrist230. In some examples, each of the drive mechanisms 250 may be a cabledisposed inside a hollow sheath or lumen in a Bowden cable likeconfiguration. In some examples, the cable and/or the inside of thelumen may be coated with a low-friction coating such aspolytetrafluoroethylene (PTFE) and/or the like. In some examples, as theproximal end of each of the cables is pulled and/or pushed inside drivesystem 240, such as by wrapping and/or unwrapping the cable about acapstan or shaft, the distal end of the cable moves accordingly andapplies a suitable force and/or torque to adjust one of the DOFs of endeffector 220, articulated wrist 230, and/or surgical instrument 200.

FIG. 3 is a simplified perspective diagram of the distal end of surgicalinstrument 200 according to some embodiments. As shown in FIG. 3 , thedistal end of surgical instrument 200 is depicted so as to showadditional details of end effector 220, articulated wrist 230, and drivemechanisms 250. In more detail, end effector 220 includes opposing jaws310 shown in an open position. Jaws 310 are configured to move betweenopen and closed positions so that end effector 220 may be used during aprocedure to grip and release tissue and/or other structures, such assutures, located at the surgical site. In some examples, jaws 310 may beoperated together as a single unit with both jaws 310 opening and/orclosing at the same time. In some examples, jaws 310 may be openedand/or closed independently so that, for example, one jaw 310 could beheld steady which the other jaw 310 may be opened and/or closed.

FIG. 3 shows that a gripping surface on an inside of each of jaws 310includes a corresponding groove 320, which may act as a guide for acutting blade 330, although the groove 320 may be omitted from one ormore of jaws 310. As cutting blade 330 is extended toward the distal endof end effector 220 and/or retracted toward the proximal end of endeffector 220, each of the grooves 320 may aid in the alignment and/orpositioning of cutting blade 330 during a cutting operation. Extractionand/or retraction of cutting blade 330 is accomplished using a drivecomponent 340 to which cutting blade 330 is attached. In some examples,drive component 340 pushes on cutting blade 330 to extend cutting blade330 and pulls on cutting blade 330 to retract cutting blade 330. Use andpositioning of cutting blade 330 is shown in FIGS. 4A-4C, which aresimplified cut-away diagrams of end effector 220 according to someembodiments. FIG. 4A shows the relationship between cutting blade 330and drive component 340.

End effector 220 further includes a garage feature 350 located at aproximal end of jaws 310. Garage feature 350 includes an opening throughwhich both drive component 340 and cutting blade 330 may pass. Garagefeature 350 is configured to provide a safe storage area for cuttingblade 330 when cutting blade 330 is not in use. Thus, when cutting blade330 is not actively being used as part of a cutting operation, endeffector 220 is configured so that cutting blade 330 may be retractedinto garage feature 350 in a “garaged” or stored position in whichcutting blade 330 is recessed proximally behind jaws 310 as shown inFIG. 4B. Cutting blade 330 may additionally be extended to a position inwhich cutting blade 330 is positioned at or near a distal end of one ofthe grooves 320 as shown in FIG. 4C. In some examples, the positioningof cutting blade 330 as shown in FIG. 4C may correspond to a position ofcutting blade 330 during a cutting operation.

In some examples, end effector 220 and surgical instrument 200 aredesigned so that the default or home position of cutting blade 330 iswithin garage feature 350. This arrangement of garage feature 350 mayprovide several features to end effector 220. In some examples, whencutting blade 330 is retracted into garage feature 350, the sharpcutting edge of cutting blade 330 is effectively sheathed so thatcutting blade 330 is unlikely to accidentally cut tissue during aprocedure and/or medical personnel handling surgical instrument 200and/or end effector 220 before and/or after a procedure. In someexamples, when cutting blade 330 is retracted into garage feature 350,cutting blade 330 may also be protected from damage, such as accidentaldulling, when cutting blade 330 is not actively being used to cut.

Referring back to FIG. 3 , in some embodiments, the gripping surface onthe inside of each of jaws 310 may further include one or more optionalelectrodes 360. In some examples, electrodes 360 may be used to deliverelectrosurgical energy to fuse tissue being held between jaws 310. Insome examples, electrodes 360 may provide an electro-cautery, fusing,and/or sealing feature to end effector 220 so that tissue may be cutand/or fused/sealed using the same surgical tool 200.

In some embodiments, operation of jaws 310, cutting blade 330, and/orthe joints of articulated wrist 230 may be accomplished usingcorresponding ones of the drive mechanisms 250. In some examples, whenjaws 310 are operated independently, a distal end of two of the drivemechanisms 250 (one for each of jaws 310) may be coupled to a respectivejaw 310 so that as the corresponding drive mechanism 250 applies a pulland/or a pushing force (for example, using a cable, lead screw, and/orthe like), the respective jaw 310 may be opened and/or closed. In someexamples, when jaws 310 are operated together, both jaws 310 may becoupled to the distal end of the same drive mechanism 250. In someexamples, drive component 340 may be coupled to a distal end of acorresponding drive mechanism 250 so that forces and/or torques appliedto the corresponding drive mechanism 250 may be transferred to the pushand/or pull motion of drive component 340. In some examples, additionaldrive mechanisms 350 may be used to operate the roll, pitch, and/or yawDOFs in articulated wrist 230.

FIG. 5 is a simplified perspective diagram of a drive unit 500 for adegree of freedom according to some embodiments. According to someembodiments, drive unit 500 may be representative of a portion of thecomponents in drive system 240 of FIG. 2 . As shown in FIG. 5 , driveunit 500 is based on a rotational actuation approach in which a capstan510 is rotated to actuate a DOF. Capstan 510 is coupled to a drive shaft520 which may be the drive shaft of a motor, servo, active actuator,hydraulic actuator, pneumatic actuator, and/or the like (not shown). Astorque is applied to drive shaft 520 and drive shaft 520 and capstan 510are rotated, a cable 530 attached to capstan 510 and/or drive shaft 520may be further wrapped around and/or unwrapped from around capstan 510and/or drive shaft 520. When cable 530 is attached to the proximal endof a corresponding drive mechanism, such as any of drive mechanisms 250,the wrapping and unwrapping of the cable may translate intocorresponding pulling and pushing forces and/or torques that may beapplied to a DOF of an end effector located at the distal end of thedrive mechanism. In some examples, rotation of capstan 510 and driveshaft 520 and the corresponding wrapping and/or unwrapping of cable 530may result in opening and/or closing of gripper jaws such as jaws 310,extending and/or retracting of a cutting blade such as cutting blade330, flexing and/or unflexing of articulated wrist joints, and/or thelike. In some examples, monitoring a rotation angle and/or rotationalvelocity of capstan 510 and/or drive shaft 520 may also provide anindication of a current position and/or velocity of the correspondingDOF coupled to cable 530 through the corresponding drive mechanism.Thus, when drive unit 500 is used in conjunction with the DOFs ofsurgical instrument 200, the rotation angle and/or rotational velocityof capstan 510 and/or drive shaft 520 may provide useful feedback on theangle to which jaws 310 are opened, the position of cutting blade 330,and/or the pitch and/or yaw angle of articulated wrist 230 depending onwhich of the drive mechanisms 250 cable 530 is coupled.

Because it is often desirable for a DOF in an end effector to beconfigured with a default, rest, and/or home position when the DOF isnot being actuated, in some embodiments a drive unit, such as drive unit500 may include some type of resistive and/or restraining mechanism toreturn drive unit 500 to a corresponding home position. In someexamples, use of a home position for a DOF may support configuration ofa surgical instrument, such as surgical instrument 200, where grippingjaws are automatically closed and/or mostly closed, cutting blades areretracted into a garage feature, articulated wrist joints arestraightened, and/or the like. As shown in FIG. 5 , drive unit 500includes a restraining mechanism in the form of a torsion spring 540.Torsion spring 540 is shown attached at one end 550 to capstan 510 andwrapped around capstan 510. As capstan 510 is rotated, a second end 560of torsion spring 540 may freely rotate until it rotates up against astop 570 that may be part of a body of drive unit 500. As capstan 510continues to rotate after the second end 560 of torsion spring 540 isagainst stop 570, torsion spring 540 will begin to provide a restrainingand/or return to home force and/or torque to capstan 510 as dictated bythe amount of rotation of capstan 510 and a spring constant of torsionspring 540. Thus, as greater amounts of rotation are applied to capstan510, torsion spring 540 applies increasing return to home force and/ortorque to capstan 510. It is this return to home force and/or torque oncapstan 510 that may be used, for example, to close the gripping jaws,retract the cutting blade, and/or straighten the articulated wristjoints.

Although FIG. 5 shows the restraining mechanism as a torsion springwrapped around capstan 510, one of ordinary skill would recognize otherpossible restraining mechanisms and/or configurations for therestraining mechanisms to accomplish a similar restraining/return tohome function. In some examples, the body of drive unit 500 may furtherinclude a second stop to provide a return to home force and/or torque tocapstan 510 in an opposite direction to the return to home force and/ortorque resulting from stop 570. In some examples, the second end 560 oftorsion spring 540 may be mounted to the body of drive unit 500 so thatno free movement of torsion spring 540 is permitted before torsionspring 540 begins applying return to home force and/or torque to capstan510 and/or torsion spring 540 applies at least some return to home forceand/or torque to capstan 510 even without rotation of capstan 510.

According to some embodiments, a cutting operation using a cutting tool,such as surgical instrument 200 with cutting blade 330 of FIGS. 3 and4A-4C, typically involves a multi-phase operation. For example, acutting operation may be accomplished by teleoperating an articulatedarm to place end effector 220 in proximity to the tissue of interest.Articulated wrist 230 and jaws 310 may then be used to grasp the tissueof interest. Once the tissue of interest is held, a drive unit, such asdrive unit 500, may be used to initiate a cutting action involving rapidextension of cutting blade 330 in a distal direction, holding cuttingblade 330 at the extended position, and then retracting cutting blade330 in a proximal direction until cutting blade 330 is returned towithin garage feature 350. During the extension and retraction, cuttingblade 330 may be guided by grooves 320 in jaws 310 so that the resultingcut occurs in a substantially straight line along the length of jaws310.

In some cases, the cutting operation may not proceed as planned. In someexamples, a blade exposure may occur where cutting blade 330 is not ableto return to the home position within garage feature 350. In someexamples, a blade exposure may occur when tissue and/or other debrisinterfere with the path of cutting blade 330 toward garage featurepreventing retraction of cutting blade 330 into garage feature 350during the retraction phase of the cutting operation. In some examples,a blade exposure may occur when cutting blade 330 twists and/or comesout of grooves 320. This may occur due to twisting force or torsion oncutting blade 330 caused by tissue, other debris, torsion forces fromdrive component 340 and/or drive mechanism 250, and/or the like. In someexamples, preventing and/or reducing blade exposures is generally a goodidea as it is not always possible to correct the blade exposure andretract the cutting blade into the garage without first extractingsurgical instrument 200 and end effector 220 from within the patient.

Careful design and/or operation of the end effector and/or the cuttingblade may be used to reduce the likelihood of blade exposures. FIGS.6A-6E are simplified diagrams of various side and front cut-away viewsof end effector and cutting blade configurations according to someembodiments. FIGS. 6A and 6B are a simplified side and front cut-awayview of an end effector 600 with a band-style cutting blade 630 that maybe used to reduce blade exposures according to some embodiments. Asshown in FIGS. 6A and 6B, end effector 600 includes jaws 610 that may beopened and closed to grasp tissue and other structures. FIGS. 6A and 6Bshow that a gripping face of each of jaws 610 may include a groove orslot 620 that may be used to guide band-style cutting blade 630 duringthe extension and retraction of band-style cutting blade 630, howevergroove 620 may be omitted from one or more of the gripping faces. Theforces and/or torques used to extend and retract band-style cuttingblade 630 are transmitted to band-style cutting blade 630 via drivecomponent 640, which is generally similar to drive component 340.

As the front cut-away view of FIG. 6B shows, band-style cutting blade630 may slide along the length of grooves 620 and may also slide up anddown within grooves 620. Band-style cutting blade 630 includes a longblade that extends well into the proximal ends of end effector 600. Thelength of the long blade is selected so that, during the extension andretraction of the cutting operation, at least a portion of band-stylecutting blade is designed to remain within grooves 620 at the proximalend of grooves 620 and jaws 610.

According to some embodiments, band-style cutting blade 630 of endeffector 600 may be subject to several drawbacks that limit itseffectiveness as a cutting tool. In some examples, the length of thelong blade may interfere with the operation of jaws 610. In someexamples, the length of the long blade may also preclude the use of anarticulated wrist, such as articulated wrist 230, as the long blade mayprevent flexing of the articulated wrist until the articulated wrist islocated a longer than desirable distance from jaws 610. In someexamples, when a blade exposure does occur using band-style cuttingblade 630, the large size and long length of band-style cutting blade630 may significantly interfere with the ability to close jaws 610and/or clear the blade exposure without first removing end effector 600from within the patient.

FIG. 6C is a simplified front cut-away view of an end effector 650 usingan I-beam style cutting blade 680 according to some embodiments. Asshown in FIG. 6C, jaws 660 each include a large slot 670 that includeboth an opening to a gripping surface of a respective jaw 660, but alsoinclude a widened slot area within the respective jaw 660. The upper andlower ends of I-beam style cutting blade 680 each include a widened endcap 690 that is larger in size than the opening to the gripping surface.These widened end caps 690 prevent the upper and lower ends of I-beamstyle cutting blade 680 from coming out of slots 670. Alternatively,when only one of jaws 660 includes large slot 670, a T-beam stylecutting blade may be used instead of an I-beam style cutting blade.

According to some embodiments, I-beam style cutting blade 680 of endeffector 650 may be subject to several drawbacks that limit itseffectiveness as a cutting tool. In some examples, a height of slot 670may unreasonably increase the cross section of end effector 650 so thatit is not as useful as part of a minimally-invasive surgical instrument.In some examples, I-beam style cutting blade 680 may not be usable aspart of a combined cutting and fusing or sealing end effector as it maynot be possible to retract I-beam style cutting blade 680 completelyfrom slots 670 as it may be difficult to reinsert end caps 690 intoslots 670 after doing so. In some examples, when a blade exposure doesoccur using I-beam style cutting blade 680, such as due to tissue and/orother debris, end caps 690 act so as to lock jaws 660 in a closed and/orpartially closed position. In some examples, when jaws 660 become lockedwhile they are still gripping tissue, it may not be possible to removeend effector 650 from the patient without doing so surgically.

FIGS. 6D and 6E are simplified side and front cut-away views of endeffector 220 from FIGS. 2, 3, and 4A-4C according to some embodiments.As described previously with respect to FIGS. 3 and 4A-4C, end effector220 includes jaws 310 that may be opened and closed to grasp tissue andother structures. A gripping face of each of jaws 310 includes a grooveor slot 320 that may be used to guide cutting blade 330 during theextension and retraction of cutting blade 330. The forces and/or torquesused to extend and retract cutting blade 330 are transmitted to cuttingblade 330 via drive component 340.

As the front cut-away view of FIG. 6E shows cutting blade 330 may slidealong the length of grooves 320 and may also slide up and down withingrooves 320. As shown, cutting blade 330 includes a much shorter bladethan band-style cutting blade 630 so that end effector 220 may maintaina small cross-section and may also be used with articulated wrist 230.And even though the shorter blade of cutting blade 330 may increase thelikelihood of a blade exposure relative to band-style blade 630 orI-beam style blade 680, the shorter blade may also improve thelikelihood that a blade exposure may be cleared without removing endeffector 220 from within the patient. In some examples, this is possiblebecause the shorter blade may be easier to retract within garage feature350 even though cutting blade 330 is not aligned with grooves 320.

According to some embodiments, the likelihood of blade exposures may bereduced when using cutting blade 330 through proper operation of cuttingblade 330 and end effector 220. In some examples, blade exposures may bereduced by preventing and/or restricting operation of cutting blade 330based on a jaw angle of jaws 310. FIGS. 7A and 7B are simplifieddiagrams of models of a probability of blade exposure according to someembodiments. FIG. 7A depicts an example model 700 of a probability ofblade exposure versus jaw angle for two possible lengths of cuttingblade extension. Curves 710 and 720 both show a relatively lowprobability of blade exposure for narrow jaw angles, a region where theprobability of a blade exposure increases rapidly with wider jaw angle,and a saturation region where the probability of blade exposure hits amaximum probability. Curve 710 corresponds to a case where the cuttingblade is extended a longer distance than curve 720.

FIG. 7B depicts an example model 750 of cutting blade extension lengthversus jaw angle for two possible probabilities of blade exposure.Curves 760 and 770 both show a region where a full length cutting bladeextension is possible at low jaw angles, a region where the length ofcutting blade extension has to diminish rapidly as jaw angle increasesto maintain a constant probability of blade exposure, and a region wherelittle or no cutting blade extension is possible due to the wideness ofthe jaw angle without an unacceptable probability of blade exposureoccurring. Curve 760 corresponds to a case where a higher tolerance(i.e., a higher probability) of blade exposure is permitted relative tocurve 770.

Anecdotal evidence suggests that surgeons are willing to tolerate acertain likelihood that a blade exposure may occur in order to be ableto cut thicker tissue that is held within the gripping jaws of thecutting tool. Consistent with this observation and according to someembodiments, the models and curves of FIGS. 7A and/or 7B may be used inone of two ways to manage the likelihood of blade exposure during acutting operation.

In some examples, model 700 of FIG. 7A may be used to determine amaximum jaw angle for which cutting lengths of a predetermined distanceare permitted. During operation of the cutting tool, cuts of thepredetermined distance may be prohibited when the jaw angle exceeds themaximum jaw angle. In some examples, when the cutting length is 18 mm,the cutting blade 330 is 2.54 mm tall, and the tolerance for bladeexposures is 10%, the maximum jaw angle may be approximately 7 degrees.

In some examples, model 750 of FIG. 7B may be used to limit a maximumcutting length based on the current jaw angle. During operation of thecutting tool, the jaw angle may be measured and, based on a tolerancefor blade exposures, the measured jaw angle may be limited to themaximum cutting length.

Whether model 700 is used to prevent a cutting operation or model 750 isused to limit the cutting length of the cutting operation, the controlapplication, such as control application 170 supervising and/orimplementing the cutting operation uses a measurement of the current jawangle to make the cut/no-cut decision and/or the cutting lengthdetermination. According to some embodiments, measurement of the jawangle may not always be as accurate as desired to support these cuttingdeterminations. As described previously with respect to FIG. 5 , the jawangle of the end effector, such as end effector 220, may, like the otherDOFs of the end effector, be measured indirectly. In the examples, ofFIG. 5 , the jaw angle may be measured based on a rotation angle of thecorresponding capstan 510 and/or drive shaft 520 from the one (joint jawcontrol) or two (independent jaw control) corresponding drive units 500for the gripper jaws of the end effector. In some examples, as thearticulated wrist flexes, the drive mechanism(s) used to operator thegripper jaws may be subject to bending and/or movement within the hollowshaft (e.g., shaft 210) of the surgical instrument. As the drivemechanism(s) bend and/or move an effective distance, as seen by thedrive mechanism, may change between the distal end at the cutting bladeand the proximal end at the drive unit. Thus, to obtain sufficientaccuracy in the determination of the jaw angle, the jaw angle may haveto be corrected based on the flex angle(s) of the articulated wristand/or roll of the input shaft.

FIG. 8 is a simplified diagram of an exemplary relationship betweenactual and measured jaw angle according to some embodiments. FIG. 8includes a scatter plot 800 from data collected using a surgicalinstrument consistent with surgical instrument 200. An end effectorconsistent with end effector 220 was used to grasp materials while anarticulated wrist consistent with articulated wrist 230 was flexed tovarious combinations of pitch and yaw angles. At each of thecombinations of pitch and yaw angles, an actual jaw angle between thegripping jaws was measured as represented by the lighter upper points inscatter plot 800. At each of the combinations of pitch and yaw angles,the jaw angle as measured at the drive unit for the gripping jaws wasrecorded as represented by the darker lower points in scatter plot 800.As shown in scatter plot 800, as both the pitch and yaw angles of thearticulated wrist deviate from an angle of zero (corresponding to noflex in the articulated wrist and alignment of the end effector with theshaft of the surgical instrument) a greater divergence between actualand measured jaw angle occurred.

The data of scatter plot 800 was then matched to various models todetermine a suitable model for the relationship and/or or functionbetween actual jaw angle and measured jaw angle as pitch and yaw angleare varied. Experimentation indicated that a linear correction modelconsistent with Eq. 1 could be used to model the relationship betweenactual and measured jaw angle with a coefficient of determination or R²value in excess of 0.95.Actual jaw angle=measured jaw angle+C ₀ +C ₁*|roll|+C ₂*|pitch|+C₃*|yaw|  Eq. 1

In some examples, the C₀, C₁, C₂, and C₃ coefficients may be modeledover a collection of surgical instruments or individually for eachsurgical instrument, with the coefficient values being recorded so thatthey are able to be accessed at run time based on an identifier, such asa serial number, of the corresponding surgical instrument. For oneexample of a surgical instrument consistent with surgical instrument200, C₀ was found to be 0.000, C₁ was found to be 0.000, C₂ was found tobe 0.062, and C₃ was found to be 0.069. The differences between C₂ andC₃ are due to differences in the design of the pitch and yaw joints aswell as the location of the yaw joint more distal to the pitch joint.

FIG. 9 is a simplified diagram of a method 900 for performing a cuttingoperation according to some embodiments. One or more of the processes910-970 of method 900 may be implemented, at least in part, in the formof executable code stored on non-transient, tangible, machine readablemedia that when run by one or more processors (e.g., the processor 150in control unit 140) may cause the one or more processors to perform oneor more of the processes 910-970. In some embodiments, method 900 may beperformed by an application, such as control application 170. In someembodiments, method 900 may be used to restrict and/or limit themovement of a cutting blade, such as cutting blade 330, based on anangle between gripper jaws, such as jaws 310, and flex in an articulatedwrist, such as articulated wrist 230, of a surgical instrument, such assurgical instrument 200. In some embodiments, the cutting operation ofmethod 900 may be performed according to models of FIGS. 7A, 7B, and 8 .In some embodiments, drive components such as those described in FIGS.2, 3, 4A-4C, 5, 6D and/or 6E may be used during the performance ofmethod 900 to determine the angle between the gripper jaws so as torestrict and/or limit the movement of the cutting blade.

At a process 910, jaws of a surgical instrument are operated. In someexamples, a surgeon and/or other medical personnel may use one or morecontrols of an operator console to position and/or operate the jaws,such as jaws 310, of the surgical instrument. In some examples, thesurgeon and/or other medical personnel may manipulate one or more mastercontrols, such as one or more master manipulators, levers, pedals,switches, keys, knobs, triggers, and/or the like to teleoperate the jawsto position them around appropriate tissue and/or other structures inpreparation for a cutting operation. In some examples, the jaws may beoperated to control their position and/or orientation as well as toadjust an angle between the jaws. In some examples, this operation mayinclude adjusting a level of flex in an articulated wrist, such asarticulated wrist 230, to orient the jaws as desired.

At a process 920, a cut command is received. In some examples, a surgeonand/or other personnel may request that a cutting operation take place.In some examples, the cutting operation may be requested using one ormore master controls, such as one or more master manipulators, levers,pedals, switches, keys, knobs, triggers, and/or the like located on anoperator console. In some examples, the requested cutting operation maybe received by a control application, such as control application 170,via an interrupt, an input polling operation, an API call, and/or thelike.

At a process 930, the jaw angle is measured. In some examples, the jawangle may be measured using one of more position and/or rotationsensors. In some examples, the sensors may be located proximal to thejaws and may be configured to measure the jaw angle indirectly. In someexamples, the sensors may be associated with one or more drive units,such as drive unit 500, that may be used to manipulate the DOF(s) of thejaws. In some examples, the sensors may measure a rotation angle of acapstan, such as capstan 510, and/or a rotation angle of a drive shaft,such as drive shaft 520. In some examples, when the jaws are controlledtogether, the jaw angle may be measured using the single drive unit forthe jaws. In some examples, when the jaws are controlled independently,the jaw angle of each of the jaws may be measured separately and thencombined to determine a composite measured jaw angle.

At a process 940, wrist articulation is measured. In some examples, thewrist articulation may be measured using one of more position and/orrotation sensors. In some examples, the sensors may be located proximalto the articulated wrist and may be configured to measure each of thearticulation angles, such as pitch and/or yaw, of the articulated wristindirectly. In some examples, the sensors may be associated with one ormore drive units, such as drive unit 500, that may be used to manipulatethe respective DOF for each of the joints of the articulated wrist. Insome examples, the sensors may measure a rotation angle of a capstan,such as capstan 510, and/or a rotation angle of a drive shaft, such asdrive shaft 520.

At a process 950, the jaw angle is corrected based on the wristarticulation. Using the jaw angle measured during process 930 and thewrist articulation measured during process 940, a corrected value forthe jaw angle may be determined by the control application. In someexamples, a jaw angle correction model, such as the jaw angle correctionmodel of FIG. 8 and/or Equation 1 may be used to correct the jaw angle.In some examples, the jaw angle correction model may be determined basedon a type of the surgical instrument and/or may be determined based onan identifier, such as a serial number, associated with the surgicalinstrument.

At a process 960, the cutting operation is restricted based on thecorrected jaw angle. In some examples, the corrected jaw angle asdetermined during process 950 may be combined with a configurabletolerance for blade exposures to determine whether the cutting operationis to be restricted. Depending upon whether partial length cuts arepermitted the cutting operation may be prevented from occurring and/orrestricted to a maximum cutting length. In some examples, when partiallength cuts are not permitted, the corrected jaw angle, the tolerancefor blade exposures, and a desired cutting length are applied to amodel, such as model 700 of FIG. 7A, to determine whether the correctedjaw angle is larger than a maximum permitted jaw angle. When thecorrected jaw angle is larger than a maximum permitted jaw angle or jawangle threshold the cutting operation is restricted to prevent it fromoccurring and/or a maximum permissible cutting length is set to zero.When the corrected jaw angle is equal to or smaller than the maximumpermitted jaw angle, the cutting operation is not restricted and/or themaximum permissible cutting length is set to a full length cut. In someexamples, when partial length cuts are permitted, the corrected jawangle and the tolerance for blade exposures are applied to a model, suchas model 750 of FIG. 7B, to determine the maximum permissible cuttinglength. The cutting operation is then restricted so that the cuttingblade is not extended beyond the maximum permissible cutting length.

In some examples, when the cutting length is restricted, an audio,visual, and/or textual alert may be provided to the surgeon and/or othermedical personnel to indicate that the cutting operation maximumpermitted jaw angle has been exceeded when partial cuts are not allowedand/or when the cutting length is reduced to less than a full lengthcut.

At a process 970, a cutting operation is performed based on the cuttingrestrictions. In some examples, the cutting operation may be performedby extending the cutting blade and then retracing the cutting blade backinto a garage. In some examples, the cutting operation may includedriving the cutting blade according to a positional profile that may beadjusted to include a maximum extension based on the maximum cuttinglength, if any, determined during process 960. In some examples, thecutting blade may be extended and/or retracted based on force and/ortorque applied to the cutting blade by a drive component, a drivemechanism, a drive unit, and/or an actuator such as a motor, solenoid,servo, active actuator, hydraulic actuator, pneumatic actuator, and/orthe like. In some examples, when the maximum permissible cutting lengthis zero or the cutting operation is not permitted, process 970 may beskipped.

In some examples, the cutting operation may be monitored during process970. In some examples, the actual position of the cutting blade and/orthe drive unit for the cutting blade may be monitored using one or moresensors to determine whether the cutting blade and/or the drive unit areable to extend and/or retract the cutting blade as desired during thecutting operation. In some examples, when the cutting blade and/or thedrive unit are not able to follow the extension and/or retraction withina predefined tolerance of a positional profile, an audio, visual, and/ortextual alert may be provided to the surgeon and/or other medicalpersonnel to indicate that the cutting operation may not have beensuccessful. In some examples, the cutting operation may not besuccessful when the cutting blade is not able to extend to the maximumpermissible cutting length. In some examples, the cutting operation maynot be successful when the cutting blade becomes exposed and cannotreturn to the garage. In some examples, a warning and/or an alert usingone or more audio, visual, and/or textual alerts may also be issued whenany of the extracting and/or retracting operations reach a correspondingforce and/or torque limit.

After the cutting operation is completed during process 970, another cutmay be performed by returning to process 920 and/or the jaws may berepositioned before performing another cutting operation by returning toprocess 910.

Some examples of control units, such as control unit 140 may includenon-transient, tangible, machine readable media that include executablecode that when run by one or more processors (e.g., processor 150) maycause the one or more processors to perform the processes of method 900.Some common forms of machine readable media that may include theprocesses of method 900 are, for example, floppy disk, flexible disk,hard disk, magnetic tape, any other magnetic medium, CD-ROM, any otheroptical medium, punch cards, paper tape, any other physical medium withpatterns of holes, RAM, PROM, EPROM, FLASH-EPROM, any other memory chipor cartridge, and/or any other medium from which a processor or computeris adapted to read.

Although illustrative embodiments have been shown and described, a widerange of modification, change and substitution is contemplated in theforegoing disclosure and in some instances, some features of theembodiments may be employed without a corresponding use of otherfeatures. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications. Thus, the scope of theinvention should be limited only by the following claims, and it isappropriate that the claims be construed broadly and in a mannerconsistent with the scope of the embodiments disclosed herein.

What is claimed is:
 1. A computer-assisted device comprising: one ormore processors; and a drive system comprising one or more drive unitsconfigured to be coupled to a cutting instrument, wherein the one ormore processors are configured to: measure, using one or more firstsensors, a jaw angle between gripping jaws of an end effector of thecutting instrument; measure, using one or more second sensors,articulation of an articulated wrist coupling the end effector to ashaft of the cutting instrument; correct the jaw angle based on thearticulation of the articulated wrist; determine a cutting length basedon the corrected jaw angle; and perform, using the drive system, acutting operation according to the cutting length.
 2. Thecomputer-assisted device of claim 1, wherein the cutting operationcomprises an extension and a retraction of a cutting blade.
 3. Thecomputer-assisted device of claim 1, wherein the jaw angle is measuredat the drive system.
 4. The computer-assisted device of claim 1, whereinthe articulation of the articulated wrist is measured at the drivesystem.
 5. The computer-assisted device of claim 1, wherein the cuttinglength is less than a full-length cutting length.
 6. Thecomputer-assisted device of claim 1, wherein to correct the jaw angle,the one or more processors are configured to adjust the measured jawangle based on a correction model.
 7. The computer-assisted device ofclaim 6, wherein the correction model is linear.
 8. Thecomputer-assisted device of claim 1, wherein the articulation of thearticulated wrist comprises one or more of a pitch angle or a yaw angle.9. The computer-assisted device of claim 8, wherein to correct the jawangle, the one or more processors are configured to adjust the measuredjaw angle proportional to one or more of an absolute value of the pitchangle or an absolute value of the yaw angle.
 10. The computer-assisteddevice of claim 1, wherein the one or more processors are furtherconfigured to: determine a restriction on the cutting operation based onthe corrected jaw angle; and perform or prevent the cutting operationaccording to the restriction.
 11. The computer-assisted device of claim10, wherein the restriction on the cutting operation is to prevent thecutting operation when the corrected jaw angle is greater than a jawangle threshold.
 12. A method comprising: measuring, by one or moreprocessors and using one or more first sensors, a jaw angle betweengripping jaws of an end effector of a cutting instrument; measuring, bythe one or more processors and using one or more second sensors,articulation of an articulated wrist coupling the end effector to ashaft of the cutting instrument; correcting, by the one or moreprocessors, the jaw angle based on the articulation of the articulatedwrist; determining, by the one or more processors, a cutting lengthbased on the corrected jaw angle; and performing, using a drive systemcomprising one or more drive units coupled to the cutting instrument, acutting operation according to the cutting length.
 13. The method ofclaim 12, wherein the cutting length is less than a full-length cuttinglength.
 14. The method of claim 12, wherein: the articulation of thearticulated wrist comprises one or more of a pitch angle or a yaw angle;and correcting the jaw angle comprises adjusting the measured jaw angleproportional to one or more of an absolute value of the pitch angle oran absolute value of the yaw angle.
 15. The method of claim 12, furthercomprising measuring the jaw angle at the drive system.
 16. The methodof claim 12, further comprising measuring the articulation of thearticulated wrist at the drive system.
 17. A non-transitorymachine-readable medium comprising a plurality of machine-readableinstructions which when executed by one or more processors associatedwith a computer-assisted device are adapted to cause the one or moreprocessors to perform a method comprising: measuring, using one or morefirst sensors, a jaw angle between gripping jaws of an end effector of acutting instrument; measuring, using one or more second sensors,articulation of an articulated wrist coupling the end effector to ashaft of the cutting instrument; correcting the jaw angle based on thearticulation of the articulated wrist; determining a cutting lengthbased on the corrected jaw angle; and performing, using a drive systemcomprising one or more drive units coupled to the cutting instrument, acutting operation according to the cutting length.
 18. Thenon-transitory machine-readable medium of claim 17, wherein the cuttinglength is less than a full-length cutting length.
 19. The non-transitorymachine-readable medium of claim 17, wherein: the articulation of thearticulated wrist comprises one or more of a pitch angle or a yaw angle;and correcting the jaw angle comprises adjusting the measured jaw angleproportional to one or more of an absolute value of the pitch angle oran absolute value of the yaw angle.
 20. The non-transitorymachine-readable medium of claim 17, further comprising: measuring thejaw angle at the drive system; and measuring the articulation of thearticulated wrist at the drive system.